1. Field of the Invention
The present invention relates to an image capture apparatus and a focus adjustment method in which a focus of a taking lens is adjusted using a contrast method based on image data captured with a solid state imaging device.
2. Background Arts
Recently, digital cameras are commonly used. The digital camera incorporates a solid state imaging device such as a CCD image sensor, and records image data obtained by digital conversion of image signals, output from the solid state imaging device, in a recording medium such as a memory card. Such digital camera performs autofocus processing of a taking lens by the contrast method (hereinafter referred to as AF processing).
In the AF processing by the contrast method, a search range having a first range and a second range is set. The first range is set based on a focal distance or a luminance value. The second range is set on a near distance side or a far distance side (usually, infinity side) of the first range to compensate errors caused by temperature changes of the taking lens. The focus lens is moved, for example, from a near distance end to a far distance end of the search range, and AF evaluation values are calculated. Then, the focus lens is moved to a lens position (in-focus position) where the AF evaluation value reaches a maximum value. Thus, the focus adjustment is performed.
Taking lens miniaturized in accordance with miniaturization of the digital camera is vulnerable to temperature changes, and such temperature changes cause deviation of the in-focus position of the taking lens. To avoid this problem, there is a camera provided with a temperature sensor to detect the temperature of the taking lens (see, Japanese Patent Laid-Open Publication No. 06-160695). At the time of the focus adjustment, the position of the taking lens is corrected based on the detection result of the temperature sensor.
However, if the focus adjustment is performed by moving the focus lens within the search range having the first and second ranges as the above digital camera, detection of the in-focus position takes long time due to long moving distance of the focus lens. Since the camera disclosed in Japanese Patent Laid-Open Publication No. 06-160695 is provided with a temperature sensor, the number of parts is increased, which hinders the miniaturization of the camera and also increases cost. Moreover, optimum focus control of the taking lens cannot be achieved if the temperature sensor is not installed at a proper position.